How to attach objects to ends of bezier curves?
With the add-on Animation Nodes you can create copys of objects and automatically place them at specific locations.



The node setup shown below loops over all objects in a group with the cables in it.  


The first loop “Get Splines” returns a list of all splines in the objects.
For every spline an instance of the desired object is created.
The second loop “Place Objects” evaluates each spline at the end (Parameter 1.00) and calculates location, tangent and normal. Parameter 0.0 would evaluate the spline at the start but then you will also have to mirror the tangent vector.
The tangent and normal are used to calculate the rotation angle for the object. You might want to replace the Guide with a random vector instead of using the spline's normal so that the terminals' orientation is more realistic.